From Longman Dictionary of Contemporary Englishbumper stickerˈbumper ˌsticker noun [countable] TTCPUBLICIZE/MAKE KNOWNa small sign on the bumper of a car, with a humorous, political, or religious message
Examples from the Corpus
bumper sticker• That he ought never put a bumper sticker on a new car.• Our unsolicited advice: Cut off the dreads, peel off the bumper sticker, and just stop listening to reggae entirely. 